1. Field of the Invention
The present invention is related to a plasma display panel, and more particularly, to circuit and method for driving a plasma display panel.
2. Background of the Related Art
The plasma display panel and Liquid Crystal Display (LCD) are spotlighted as next generation displays of the greatest practical use, and, particularly, the plasma display panel has wide application as a large sized display, such as an outdoor signboard, a wall mounting type TV, a display for a movie house because the plasma display panel has a higher luminance and a wide angle of view than the LCD. FIG. 1 illustrates a system of a related art plasma display panel with a resolution of 640xc3x97480.
Referring to FIG. 1, the related art plasma display panel is provided with a panel having 640xc3x97""address electrode lines R1, G1, B1, R2, G2, B2, . . . , R639, G639, B639, R640, G640, B640, 480 scan electrode lines S1, S2,. . . , S480 vertical to the address electrode lines, and sustain electrode lines 15 of the same number as the scan electrode lines, an address electrode driving unit 50 for applying data pulses to the address electrode line 17, a scan electrode driving unit 30 for applying scan pulses and sustain pulses to the scan electrode line 14, a sustain electrode driving unit 60 for applying the sustain pulses to the sustain electrode line 15, and a microcomputer 20 for controlling the address electrode driving unit 50, the scan electrode driving unit 30, and the sustain electrode driving unit 60. As shown in FIG. 2a, the panel is provided with an upper substrate 10 and a lower substrate 10xe2x80x2, both of which are bonded together facing each other. FIG. 2b illustrates a section of the panel illustrated in FIG. 2a, with the lower substrate turned an angle of 90xc2x0 with reference to an axis vertical to a substrate plane for convenience of explanation. The upper substrate 10 is provided with successive sets of the scan electrode lines 14, each having a transparent electrode 14xe2x80x2 and a metal electrode 14xe2x80x3; and the sustain electrode lines 15, each having a transparent electrode 15xe2x80x2 and a metal electrode 15xe2x80x3, a dielectric layer 11 coated on the upper substrate having the scan electrodes and the sustain electrodes formed thereon, and a protection film 12 coated on the dielectric layer 11. And the lower electrode 10xe2x80x2 is provided with the address electrode lines 17 formed to cross the scan electrodes and the sustain electrodes, and a lower dielectric layer 18 coated on the lower substrate having the address electrode formed there under. And, there is a partition wall 19 formed between every region of the dielectric layer the address electrode lines 17 formed therein, and a fluorescent material film 13 coated on portions of the partition walls and the region of the lower dielectric layer under which the address electrode is formed. An inert gas is sealed in a space between the upper substrate and a lower substrate, to form a discharge region. Each of the address electrode lines 17 is formed continued on the lower substrate 10xe2x80x2, and, as shown in FIG. 2a, the partition wall 19 separates adjacent address electrode lines. As shown in FIG. 1, in a case of a color plasma display panel, the address electrode lines 17 are formed such that one set composed of adjacent three address electrode lines R1, G1, B1 forms one pixel. The one set of three address electrode lines 17 are adapted to be applied of data pulses for R(Red), G(Green), and B(Blue) video signals, respectively. The scan electrode lines S1, S2, S3,. . . , S480, 14 and the sustain electrode lines 15 are formed to cross the address electrode lines 17 on the upper substrate 10 disposed to face the lower substrate 10xe2x80x2, for being applied of sustain pulses as shown in FIG. 3. The sustain pulses applied to the scan electrode lines and the sustain electrode lines have opposite phases and the same frequencies. The microcomputer 20 receives a video signal and a clock signal and the like, and controls the address electrode driving unit 50, the scan electrode driving unit 30, and the sustain electrode driving unit 60 to realize an image of the video signal on the panel. The address driving unit 50, synchronous to the scan pulses, applies data pulses for the video data from the microcomputer to all address electrode lines 17 on the same time. The address electrode driving unit 50 receives the video data, and provides data pulses for selective discharge of the discharge cells. The data pulses for application to the address electrode lines 17 are illustrated in FIG. 3. The scan electrode driving unit 30 applies scan pulses to the scan electrode lines S1, S2, . . . , S480 in succession in response to a control signal from the microcomputer 20 while the sustain electrode driving unit 60 applies sustain pulses to all the sustain electrode lines 15. The control signal applied in this instance is in general called a xe2x80x98BLANKxe2x80x99 signal. The scan electrode driving unit 30 provides no scan pulses when the control signal is xe2x80x980xe2x80x99, and provides the scan pulses when the control signal is xe2x80x981xe2x80x99. The sustain pulses and the scan pulses applied to the scan electrode lines S1, S2, . . . , S480 is illustrated in FIG. 3. The sustain electrode driving unit 60 applies sustain pluses to all of the sustain electrode lines 15 at the same time. The sustain pulses applied to the sustain electrode lines have a phase opposite to a phase of the sustain pulses applied to the scan electrode lines 14. The plasma display panel is driven by discharges occurring among the electrodes, which are divided into a reset discharge period in which each of the discharge cells in the plasma display panel are initialized in response to the pulses applied to each electrode, an address discharge period in which each of the discharge cells are scanned line by line selectively, and a sustain discharge period in which a discharge in the discharge cell scanned during the address discharge period is sustained. The plasma display panel may be either a selective erasure method or a selective write method depending on characters of the discharge cell scanning in the address discharge period.
The method for driving the plasma display panel in the selective write method will be explained. During the reset discharge period, all the scan electrodes 14 and the sustain electrodes 15 in the plasma display panel are applied of a discharge voltage to cause a primary discharge in discharge regions of the discharge cells, which in turn erases all wall charges formed on the dielectric layer on the scan electrodes 14 and the sustain electrodes 15 and 15xe2x80x2. As explained, sustain pluses are always applied to the scan electrodes 14 and 14xe2x80x2 and the sustain electrodes 15. However, because a voltage of the sustain pulses applied to the scan electrodes 14 and 14xe2x80x2 and the sustain electrodes 15 and 15xe2x80x2 is lower than a discharge initiation voltage which initiates a discharge, the discharge regions in the discharge cells make no discharges. As shown in FIG. 3, the scan electrode lines 14 are applied of scan pluses in succession for one cycle of the sustain pulses. In this instance, the address electrode driving unit 50 applies data pulses to the address electrode line 17 connected to the discharge cell to be discharge according to the video data provided from the microcomputer 20. As a result, a discharge is induced in the discharge cell of the discharge cells connected to the scan electrode lines 14 applied of the scan pulses at a portion crossing the address electrode line 17 applied of data pulses, to generate a wall charge at a surface of the dielectric layer on the scan electrode 14 and the sustain electrode 15 in the discharge cell. That is, while one scan pulse is applied to one scan electrode line 14, the address electrode driving unit 50 applies data pulses determining discharge of the discharge cells connected to the one scan electrode line 14 on the same time according to the video data of one line amount provided form the microcomputer 20. For example, if it is intended to form white on all pixels connected to the one scan electrode line 14, data pulses are provided to all address electrode lines 17, to cause discharge in all the discharge cells on the one line. In this instance, it is impossible to apply scan pulses to all the scan electrode lines 14 for one cycle of the sustain pulses. Because, in order to apply scan pulses to all the scan electrode lines 14 for one cycle of the sustain pulses, intervals of the data pulses applied to the address electrode 17 would be excessively short, which may make the discharge operation unstable, inducing no discharge of the discharge cells. Therefore, the related art plasma display panel is provided with the scan electrode driving unit 30 having many driving IC""s each connected to about 40 to 120 scan electrode lines 14. And, the related art plasma display panel has a scan pulse application interval set therein such that approximately 4 data pulses are applied for one cycle of the sustain pulses.
The sustain pulses, the scan pulses, and the data pulses respectively applied during the reset discharge period, the address discharge period, and the sustain discharge period have waveforms as illustrated in FIG. 3.
The operation principle of the plasma display panel in the selective erasure method will be explained. Pulses applied to respective electrodes in the plasma display panel according to the selective erasure method are illustrated in FIG. 4.
Write pulses are applied to the scan electrodes 14, added to the sustain pulses. Then, a voltage from the write pulse and the sustain pulse to the sustain electrode 15 induces a discharge in a discharge region between the sustain electrodes 15 and the scan electrodes 14. Because a voltage between the scan pulse for the scan electrodes and the sustain pulse for the sustain electrodes is higher than the discharge initiation voltage, a wall charge is induced on the dielectric layer 11 on the sustain electrodes and the scan electrodes. As shown in FIG. 4, the scan electrode lines 14 are applied of scan pulses in succession for one cycle of the sustain pulses. In this instance, the address electrode driving unit 50 applies data pulses to the address electrode 17 connected to the discharge cell to be discharged according to the video data provided from the microcomputer 20. As a result, a discharge is induced in the discharge cell of the discharge cells connected to the scan electrode lines 14 applied of the scan pulses at a portion crossing the address electrodes 17 applied of data pulses, to erase a wall charge formed at the dielectric layers on the scan electrode 14 and the sustain electrode 15 in the discharge cell. That is, while one scan pulse is applied to one scan electrode line 14, the address electrode driving unit 50 applies data pulses determining discharge of the discharge cells connected to the one scan electrode line 14 on the same time according to the video data of one line amount provided from the microcomputer 20. For example, if it is intended to form white on all pixels connected to the one scan electrode line 14, data pulses are not provided to all address electrode lines 17 in the address electrode driving unit 50 in a plasma display panel of the selective erasure method. Opposite to this, if it is intended to form black on all pixels connected to the one scan electrode line 14, data pulses are provided to all address electrode lines 17. That is, in view of forming a portion of an image in one discharge cell, the selective write method induces a discharge in the discharge cell by the data pulses, and the selective erasure method stops a discharge in the discharge cell by the data pulses. Of the methods, in view of composing one frame of image, generally employed for forming an image on an entire display region of the plasma display panel utilizing the portions of the images in each discharge cells is a sub-field method illustrated in FIG. 5. In the sub-field method, one image displayed by the selective write method or the selective erasure method is set as one sub-field, and a number of the sub-fields are overlapped by controlling the scan electrode driving unit 30, the sustain electrode driving unit 60, and the address electrode driving unit 50, to form one complete frame. In this sub-field method, it is required to gather a number of sub-fields in succession to form one frame, of which number is the same with a number of bits of gradation of the image. That is, if one frame of image is formed on the screen in 8 bits of gradation, the number of sub-fields formed according to the sub-field method is also 8. In the sub-field method, a voltage coming from one bit of digital video signal is applied to all cells in the plasma display panel, to form a first sub-field in which all cells have the same luminances. Then, a voltage coming from the next bit of digital video signal is applied, to form a second sub-field in which all cells have the same luminances, again. In this instance, through the luminances of the discharge cells in the first sub-field are the same and the luminances of the discharge cells in the second sub-field are the same, the luminances of the first, and second sub-fields are not the same. In the sub-fields each formed by the one bit of video signal, there is a most significant sub-field by a most significant bit that has the highest luminance, a least significant sub-field by a least significant bit that has the lowest luminance, and a number of sub-fields by intermediate bits between the most significant bit and the least significant bit. For example, one frame of image with 8 bits of gradation is composed of an overlap of a first sub-field by the most significant bit, an eighth sub-field by the least significant bit, and a second, a third, a fourth, a fifth, and a sixth sub-fields of which luminances are differentiated by the six intermediate bits. In the sub-field method, such eight sub-fields are overlapped, to form one frame of perfect image by the residual image effect of a human eye.
FIG. 6 illustrates a four-division sub-field driving system in which the scan electrode driving unit has four divisions, and FIG. 7 illustrates scan pulses, sustain pulses, and data pulse in the selective erasure method in driving the four-division plasma display panel illustrated in FIG. 6.
Referring to FIG. 6, in a first address discharge interval in the four-division sub-field driving system, a first scan pulse xe2x80x98axe2x80x99 illustrated in FIG. 7 is applied to a first scan electrode line S1, a second scan pulse xe2x80x98bxe2x80x99 is applied to an 121st scan electrode line S121, a third scan pulse xe2x80x98cxe2x80x99 is applied to a 241st scan electrode line S241, and a fourth scan pulse xe2x80x98dxe2x80x99 is applied to a 361st scan electrode line S361, for addressing the discharge cells on each of the lines. Then, in a second address discharge interval, the first scan pulse xe2x80x98axe2x80x99 is applied to a second scan electrode line S2, a second scan pulse xe2x80x98bxe2x80x99 is applied to an 122nd scan electrode line S122, a third scan pulse xe2x80x98cxe2x80x99 is applied to a 242nd scan electrode line S242, and a fourth scan pulse xe2x80x98dxe2x80x99 is applied to a 362nd scan electrode line S362, for addressing the discharge cells on each of the lines. Thus, the four-division sub-field driving system illustrated in FIG. 6 proceeds the addressing until an 120th addressing discharge interval is finished, to address the discharge cells on all the scan electrode lines S1, S2, . . . , S480. A sequence of providing the scan pulses in the four-division sub-field driving system illustrated in FIG. 6, i.e., an addressing sequence is as shown in Table 1, below.
In this instance, as shown in FIG. 7, the address driving unit provides a data pulse which determines a discharge of the discharge cells connected to the scan electrode line to which a scan pulse is applied every time the scan pulse is applied in each address discharge interval. In the first address discharge interval, when the first scan pulse is applied to the first scan electrode line S1, the address driving unit applies a data pulse which determines a discharge of the discharge cells connected to the first scan electrode line S1. Then, when the second scan pulse is applied to the 121st scan electrode line S121, the address driving unit applies a data pulse which determines a discharge of the discharge cells connected to the 121st scan electrode line S121. Eventually, the address driving unit applies a data pulse of the video data for the discharge cells connected to the first scan electrode line to the address electrode lines, a data pulse of the video data for the discharge cells connected to the 121st scan electrode line to the address electrode lines, a data pulse of the video data for the discharge cells connected to the 241st scan electrode line to the address electrode lines, a data pulse of the video data for the discharge cells connected to the 361st scan electrode line to the address electrode lines, a data pulse of the video data for the discharge cells connected to the second scan electrode line to the address electrode lines, a data pulse of the video data for the discharge cells connected to the 122nd scan electrode line to the address electrode lines, a data pulse of the video data for the discharge cells connected to the 242nd scan electrode line to the address electrode lines, and a data pulse of the video data for the discharge cells connected to the 362nd scan electrode line to the address electrode lines. In the four-division sub-field system, upon completion of the first scan pulse application to the 120th scan electrode line S120 for forming a sub-field image of the most significant bit(MSB), the first scan pulse xe2x80x98axe2x80x99 is applied to the first scan pulse electrode line S1 for forming a sub-field image of the next bit, and so on in the sequence as shown in Table 1. The four-division sub-field driving system forms an image on the plasma display by applying the scan pulses to the scan electrode lines as shown in Table 1.
However, the four-division sub-field driving system shown in FIG. 6 has the following problems.
The four-division sub-field driving system shows flickers of image at an interface portion L1 of a region P1 in which the scan electrode line is addressed by the first scan pulse and a region P2 in which the scan electrode line is addressed by the second scan pulse, at an interface portion L2 of a region P2 in which the scan electrode line is addressed by the second scan pulse and a region P3 in which the scan electrode line is addressed by the third scan pulse, and at an interface portion L3 of a region P3 in which the scan electrode line is addressed by the third scan pulse and a region P4 in which the scan electrode line is addressed by the four scan pulse. The flickers occur because the discharge cells connected to the scan electrode line at each interface portion may have bits of grades different from each other, with different discharge states. For example, while the discharge cells connected to the 120th scan electrode line S120 form an image of 7 bit grade, the discharge cells connected to the 121st scan electrode line S121 may form an image of 6 bit grade.
And, an image of the plasma display panel driven by the plasma display panel driving method illustrated in FIG. 6 generates contour noises, failing to provide a stable image to users. The contour noise is a disturbance of image a watcher can notice when the watcher watches the image while the watcher moves a point of view. This contour noise occurs frequently in a moving picture with a gradation. The contour noise occurs because the watcher happens to feel as if an image grade is formed irregularly at observing different sub-fields in one frame during the watcher watches the image while the watcher moves a point of view. For example, if the watcher watches an image formed on a lower portion of the screen momentarily, while the watcher watches an image formed on an upper portion of the screen, the watcher may sense a sub-field image totally different from the sub-field image formed on the upper portion. As a result, though the plasma display panel forms images smoothly, the watcher observes flickering of the image.
Accordingly, the present invention is directed to circuit and method for driving a plasma display panel that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a circuit and method for driving a plasma display panel which can reduce flickers and contour noises which occur in a plasma display panel image, to form a stable image.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the method for diving a plasma display panel includes the step of scanning a plurality of driving regions which are divisions of the plasma display panel on the same time.
In other aspect of the present invention, there is provided a method for driving a plasma display panel including the steps of (1) applying first scan pulses to a first driving block, which is any one of the driving blocks, in every given driving cycle starting from a first scan electrode line to (n)th scan electrode line in succession, and (2) applying second scan pulses each having a given application time difference from the application time of the first scan pulse to a second driving block adjacent to the first driving block starting from (m)th scan line to a first scan line in a reverse sequence to the first scan pulses. In this instance, the second scan pulse is applied to a scan electrode line in the first driving block and the first scan pulse is applied to a scan electrode line in the second driving block in every given cycle. That is, an application sequence of the scan pulses applied to the first driving block and the second driving block is changed in turn in every given cycle.
In another aspect of the present invention, there is provided circuit for driving a plasma display panel including a panel unit having a plurality of scan electrode line and a plurality of sustain electrode lines, both arranged in parallel to each other, a plurality of address electrode lines arrange to cross the scan electrode line, with a discharge cell formed at every cross of the scan electrode lines and the address electrode lines, a plurality of driving circuit for applying driving signals different from one another to groups of scan electrode lines of a given number, a common circuit unit for applying driving signals to the sustain electrode lines, and a control unit for applying control signals to different driving units.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.